ZID atcs reports two air carriers off two different airports have flights with the same 4 digit call...

Attributes
ACN	867498
Time
Date	201001
Local Time Of Day	1201-1800
Place
Locale Reference	ZID.ARTCC
State Reference	IN
Aircraft 1
Make Model Name	EMB ERJ 145 ER&LR
Operating Under FAR Part	Part 121
Flight Phase	Climb
Route In Use	None
Flight Plan	IFR
Aircraft 2
Make Model Name	EMB ERJ 170/175 ER&LR
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Route In Use	None
Flight Plan	IFR
Person 1
Function	Enroute
Qualification	Air Traffic Control Fully Certified
Events
Anomaly	ATC Issue All Types

Narrative:

ACR1 abcd and ACR2 abcd were on my frequency at the same time and I switched ACR2 abcd to next frequency when ACR1 abcd answered; 'was that for me?' at that exact moment I realized; they had done it again. For awhile around mid november; ACR1 abcd off ZZZ1 had changed their call sign number to a non-similar three digit number. This took a long time to accomplish. However; today; I realized they are back with the old number in conflict with ACR2 abcd off ZZZ2 and in our sector 77 at the same time...why? I have been filing on this situation for some time.

Original NASA ASRS Text

Title: ZID ATCS reports two air carriers off two different airports have flights with the same 4 digit callsign that routinely enter his/her sector at the same time. This results in confusion.

Narrative: ACR1 ABCD and ACR2 ABCD were on my frequency at the same time and I switched ACR2 ABCD to next frequency when ACR1 ABCD answered; 'was that for me?' At that exact moment I realized; THEY had done it again. For awhile around mid November; ACR1 ABCD off ZZZ1 had changed their call sign number to a non-similar THREE digit number. This took a long time to accomplish. However; today; I realized they are back with the old number in conflict with ACR2 ABCD off ZZZ2 and in our sector 77 at the same time...WHY? I have been filing on this situation for some time.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

ZID atcs reports two air carriers off two different airports have flights with the same 4 digit callsign that routinely enter his/her sector at the same time. This results in confusion.